Drying apparatus



Nov, 22, 1966 H. L. sMrrH, .1R 3,286,369

DRYING APPARATUS Horace {..Smif/I, J: "1

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DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 2 Energy Distribution For 4,000 F Tungsten Frloment Quartz Lamp INVENTOR Horace L..S`mifh Jn MM BY y@ 7l@ Nov. z2, 1966 H. L. SMITH, JR 3,286,369

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 3 ATT RNEYJ' Nov. 22, 1966 H. SMITH, JR 3,286,359

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 4 BY 9.4 @Mguez/ ATTORNEYJ` Nov. 22, 1966 H. L. SMITH, JR 3,286,369

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 5 ATTORNEY` SA In'.

18 Sheets-Sheet 6 H. L. SMITH, JR

DRYING APPARATUS Nov. 22, 1966 Original Filed March 4, 1963 INV ENT OR Horace L. Smith, Jn

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DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 7 INVENTOR Horace L. Smith, In

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Nov. 22, 1966 H 1 SMH-H, JR 3,286,369

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 8 INVENTOR Horace L. Smith, Jr.

ATTO NEYJ' Nov. 22, 1966 Original Filed March 4, 1965 do N'Od M30 H. l.. SMITH, .JR 3,286,369

DRYING APPARATUS 18 Sheets-Sheet 9 Specific Humidity Lb. Wofer/LbDry Air fz gJ INVENTOR Horace L.$mith, Ja

A ORNEYS NOV. 22, 1966 H, sMrrH, JR 3,286,369

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 10 Amphfler Controller Exhous' mr Lgh Source Photo Cell INVENIOR f1 7. .Z5 Horace L. Smith, Jn

ATTORNEY@ NOV. 22, 1966 H, L, SMH-H, JR 3,286,369

DRYING APPARATUS Drignal Filed March 4, 1963 18 Sheets-Sheet 11 iii' 5,'1.

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BY g//Qznff ATTORNEYS NOV. 22, 1966 H, sMlTH, JR 3,286,369

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 12 INVENTOR Harace L. Smith, Jr:

f M BY /Qmg/ ATTORNEYS NOV. 22, 1966 H L sMlTH, JR 3,286,369

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 15 INVENTOR Hnrace L. Smil/r, Jn

MMM/M BY fa@ 9 /M ATT NEYS Nov. 22, 1966 Original Filed March 4, 1963 18 Sheets-Sheet 14 2,22 22e I Supply Fon als Press l 228 Motor Conrol Panel Exhaust Fon /238 I' Switch l J "l Exhaust Fan l 242 I 4 1 2 O I i 2 i 25o 1 l 240 l 232 H6 24|`" T' f 256 j? ne {2;2

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INVENTOR Homes L. Smit/l, Jn

ATTORNEYS Nov. 22, 1966 H. L.. SMITH, JR

DRYING APPARATUS 18 Sheets-Sheet 15 Original Filed March 4, 1963 INVENTOR Horace L. .Sm/M, Jn

Nov. 22, 1966 H. L. SMITH, .1R 3,285,359

DRYING APPARATUS Original Filed March 4, 1963 18 Sheets-Sheet 16 INVENT OR *brace L S ith, Jn gf ATTO 5 Nov. 22, 1966 H. L.. SMITH, JR

DRYING APPARATUS 18 Sheets-Sheet l 7 Original Filed March 4, 1965 IOO o4- In. Thick 7 Wave Length Microns Y MMM Afforneys INVENTOR Horace L. Smil/i, Jr.

NOV. 22, 1966 H sMlTH, JR 3,286,369

DRYING APPARATUS Original Filed March 4, 1965 18 Sheets-Sheet 18 6. Infra Red Lamp Energy Distribution @4,000F

Wave Length (AU-l maand mwwauag lnvenfar Horace L. Smfmdn A l 2 f/ ,41" wim/W United States Patent O 3,286,369 DRYING APPARATUS Horace L. Smith, Jr., Richmond, Va., assignor to Hupp Corporation, Cleveland, Ohio, a corporation of Virginia Original application Mar. 4, 1963, Ser. No. 262,569. Divided and this application Dec. 17, 1965, Ser. No. 514,471

Claims. (Cl. 34-155) This application is a division of lapplication No. 262,- 569, tiled March 4. 1963 (now Patent No. 3,237,314).

rIlhe present invention relates to methods of and apparatus for drying rapidly moving materials containing volatile constituents. More particularly, this invention relates to the rapid drying of solutions ot materials such as inks, resins and the like deposited on or impregnated into rapidly moving carriers ysuch as Webs or sheets of paper, textiles, cellophane and the like.

In recent years developments in high speed presses and printing techniques have outstripped developments in the drying art to the point that the present drying equipment used in printing installations cannot iadequately dry printed areas with suicient speed to prevent smearing or smudging when the printing presses are operated at full printing capacities. As ia result, modern high speed printing presses are usually operated at speeds well below their design limits, thus substantially reducing production rates and keeping printing costs high.

Many devices have been proposed and used to accelerate the drying of ink and other materials printed on and impregnated in paper, textiles, and other carriers. For example, it has been proposed to pass the carriers over open gas flames, to blow hot `air across `the printed areas, and to employ steam heated radiators, electric strip heaters and gas burning infrared heaters for this purpose. At best, such methods only partially `solve the problem. All fail to provide drying speeds commensurate with 4the printing capabilities of modern printing equipment and in general require use of cumbersome, bulky and expensive equipment.

Another disadvantage of prior drying techniques and apparatus is that the ycarrier may become distorted during the drying cycle. For example, in one installation a paper web printed with black `ink is discharged from a gas heated furnace at temperatures in the range of 250 F. to 300 F. and passed over water cooled rolls to reduce its temperature. A-s the web leaves the furnace and is cooled, it absorbs moisture from the atmosphere and changes dimensions, distorting the printed material.

In contrast with prior art drying apparatus, that provided by the present invention permit-s presses to be operated at their rated capacities and, in addition, substantially eliminates the distortions of material caused by existing drying equipment. `My novel drying apparatus utilizes as a heat source short Wave length radiant energy which is absorbed at different rates by inks (or other printing materials) and the materials of which the carriers are fabricated. By employing radiant energy of the proper wave length, I am able yto heat the printed or coated areas at relatively high rates to evaporate the volatile materials rapidly and at the same time limit the application of heat to 'the uncoated portions of the carriers to a sufficiently lower rrate to prevent substantial heat damage to the carriers.

The relative absorptivities of inks (or coatings) and carrier materials vary at dilferent rates with changes in the wave length of the radiant energy. As the wave length of the radiant energy is shortened, the absorption or emissivity factors of usual carrier materials decrease rapidly so that such materials absorb proportion ately less shorter wave energy than longer wave. On the 3,286,369 Patented Nov. 22, 1966 other hand, both light and dark colored inks absorb relative high proportions of incident radiant energy at the longer wave lengths. Thurs, by using -radiant energy of proper wave lengths, maximum differences between the absorption rates orf the ink and the carrier can be attained, permitting evaporation of the volatile constisb ents of the ink at a higher rate than has heretofore been attained.

The low rates at which certa-in carrier materials absorb short wave length radiant energy also decrease the quantity of `heat added 4to the material during the drying cycle and, therefore, the amount of heat which must be `removed in cooling the web, further reducing the bulki- `ness, space requirements, and costs of the necessary drying equipment. In addition, the evaporation of moisture from the carrier is minimized, decreasing shrinkage and other distortion and preventing the carrier from becoming brittle. As a result, a low and cheaper grade of carrier material may often be employed with a consequent reduction in cost.

ln my invention `the accelerated drying of printed or coated areas is accomplished by establishing a zone or zones `whe-rein `intense radiant energy is projected upon the carrier at temperatures far .above those attainable in prior art devices, and far above ythe evaporating temperatures of the solvents used in the printing, coating, or impnegnating. The radiant energy is preferably generated at peak wave lengths that produce the greatest difieren tial absorption between printed and unprinted areas with the maximum rate -of absorption in the printed areas to shorten the drying `time to a minimum to thereby maximize the output of the equipment. The heating zones are of 4a length and provide energy of intensities permitting maximum web velocity with adequate drying. Web speed-'heat output correlating controls are preferably provided to maintain the amount of heat absorbed in the printed areas substantially constant.

Since different colored inks absorb radiant energy at different rates, in multi-color printing systems such as rotogravure installations in which the difieren-t colors are printed successively, I preferably utilize adjacent each printing roll or plate a radiant energy source at an emission temperature that will result in the greatest absorption by the ink printed by that roll with `the greatest difference in energy absorption between `the printed and unprinted areas. In addition, as different ink and coating so-lvents evaporate at different rates and require dilerent amounts of heat, I preferably adjust the amount of heat supplied at each zone in accordance with the requirement of the solvent evaporating characteristics of the ink or coating to be dried in that zone. The lightest inks, which are the least absorptive and most diicult to dry, are printed on the carrier rst. Thus, these inks are at least partially dried at the station at which they are printed, and further dried at each succeeding station. As a result, the least absorptive inks are exposed to the radiant energy for the longest periods, ensuring that all inks laid on the carrie-r will be properly dried during the drying cycle and will provide clear impressions of each diilerent color without smudging of the final image.

Another advantage of my invention is that substantially uniform drying of light and dark colored inks printed substantially simultaneously on a single carrier can be obtained. In this type of printing process at somewhat longer wave lengths, the lighter color inks have higher absorptivity coefficients than they do at shorter wave lengths. At such wave lengths, the differential absorptivity between the light and dark colored inks is therefore minimized so they dry at substantially uniform rates. Although the differential in absorptivity between the inks and carrier may be decreased at the longer wave lengths, there will still be a suiciently large differential that the inks can be rapidly dried without overheating the carrier.

My invention is readily adaptable to existing installations and, in conventional installations employing heated drying rolls, effectually converts the heated rolls into heat equalizing devices which initially aid in heating the ink or coating to be dried, but convey heat away from the carrier to prevent heat damage if the temperature of the carrier rises above that of the rolls.

My invention also provides for cooling the dried carrier, for increasing its moisture content, and for removing fumes and vapors from the press room or other enclosure in which the drying installation is located. This I accomplish by the use of a novel air cooling unit. The air cooling unit preferably includes an air washer to increase the humidity of the cooling air, thereby adding to its heat carrying capacity and its ability to transfer moisture to the carrier. In its preferred embodiment the air cooling unit effects a tlow of air from the press room or other enclosure through the drying apparatus and into an exhaust duct system. The continuous removal of air from the enclosure ensures against the es-cape of fumes and vapors from the drying apparatus into the enclosure.

In some installations it may be desirable to employ the air cooling units in pairs with the units in each pair delivering air to opposite sides of the carrier. In this arrangement, the two air cooling units cooperate to position the carrier and support it free from contact with any mechanical support. As a result, there is substantially no friction on the carrier and wet ink or coating on its lower or back side will not smudge, offset, or smear.

In other installations it will be more advantageous to employ a single air cooling unit. In this circumstance I may employ a novel air cushion support to position the sheet and prevent it from billowing. As in the dual air cooling unit arrangement, the air bearing support eliminates smudging of wet ink or coating on the back side of the carrier.

The air cooling unit may also be readily arranged to draw cooling air over the electrical connections to the radiant heaters to prevent them from overheating.

I may also employ chilled rolls in conjunction with air cooling units, utilizing the air cooling units primarily to remove vapors and fumes and the chilled rolls to extract vSensible heat from the carrier.

My invention also relates to improvements in the art of drying inks printed upon transparent webs. In this process, as exemplified by United States Patent No. 2,236,- 754 to Gurwick, a printed material is impressed on one side of a carrier of material which is substantially transparent to infrared energy. Radiant energy is then applied to the carrier to dry the printing.

The transparency to radiant energy of such carriers is dependent upon the wave length of the radiant energy and, for each such material, there is a wave length range in which available inks absorb heat at the maximum rate and in which the carrier material has the greatest transparency. In accordance `with my invention I utilize this discovery to substantially improve the apparatus and method described in Gurwicks patent by supplying the radiant energy at the wave length that produces the greatest rate of absorption by the inks and to which the carrier materials are most transparent. In this way the greatest rate of energy absorption by the inks is obtained with minimum heating of the carrier.

I have also found that a signicant increase in the efficiency of my improved film drying process can be obtained by locating a reflector on the side of the lm opposite the radiant energy source to reflect back onto the printed areas radiant energy transmitted through the lm. This results in almost all of the emitted energy being absorbed in the printed areas. This arrangement may also be advantageously employed to dry inks or coatings on papers and other carriers which are only partially transparent to the heating radiation.

In the blanket-to-blanket method of printing, the carrier is printed on and radiant heaters are preferably arranged on both sides of the carrier to obtain maximum drying. The reectors surrounding the radiant heaters function in the manner of the reector discussed above, providing maximum absorption of the emitted radiant energy.

My invention is also extremely useful in drying inks or coatings on highly reective carriers such as aluminum foil or materials with rellective, metalized surfaces. In this application of my invention radiant energy having a somewhat longer wave length is preferably employed since the absorptivity of a polished metal such as aluminum decreases as the wave length increases. By using longer wave length radiant energy, maximum differentiation between the absorptivities of the carrier and colored inks, for example, may be obtained, resulting in the most favorable ratio of drying rate to heat absorption by the carrier.

A primary object of my invention is therefore to provide novel, high speed, relatively low cost methods and apparatus for drying fast moving, printed, coated, and impregnated carriers such as sheets and webs.

Another object of my invention is to provide methods of and apparatus for drying single and multi-color inks that will enable the attainment of printing speeds commensurate 'with the maximum capabilities of existing printing equipment.

A further object of my invention is `to reduce printing space requirements, equipment, and operating costs and, at the same time, improve production rates and the quality of the printed product.

Another object of the present invention resides in the provision of novel drying apparatus and methods which will eliminate distortion of the carrier and prevent it from becoming brittle.

A specific object of the present invention resides in the provision of novel drying apparatus for and methods of drying web or sheet type carriers employing selected wave length radiant energy to evaporate volatile constituents from materials on or impregnated in the carrier.

Another object of the present invention resides in the provision of novel apparatus for drying multi-colored inks by the application of radiant energy in which the different colored inks are subjected to selected wave length radiant energy for periods varying inversely to their absorptivities.

It is another object of the present invention to provide novel methods of and apparatus for drying materials on or impregnated into sheet and web type carriers in which volatile constituents are evaporated from said materials by applying to said carrier radiant energy of a wave length resulting in the greatest differential absorptivity between the carrier and the material.

Yet another specific object of the present invention resides in the provision of novel methods of and apparatus for drying materials on or impregnated into sheet and web type carriers in which radiant heating is employed to evaporate volatile constituents from said materials and in which conductive members are maintained at a temperature below that which would damage said carrier to heat said carrier to evaporate the solvent therefrom and to act as a heat sink if the temperature of said carrier rises above said predetermined temperature to prevent heat damage to said carrier.

It is a further object of the present invention to provide improved drying apparatus having a novel air cooling unit for maintaining the humidity of the carrier constant and for removing fumes and vapors from the enclosure in which the drying apparatus is located.

A further specific object of the present invention resides in the provision of improved drying apparatus having a novel air cushion for supporting the carrier being dried on a film of air and thereby preventing it fromy smearing, smudging, or offsetting.

It is another specific object of the present invention to 

1. APPARATUS FOR DRYING MATERIALS ON A CARRIER TRAVELING AT HIGH VELOCITY, COMPRISING: (A) CASING MEANS ARRANGED ADJACENT SAID CARRIER AND EXTENDING IN THE DIRECTION OF ITS MOVEMENT; (B) RADIANT ENERGY SOURCE MEANS WITHIN SAID CASING MEANS OPERABLE AT A TEMPERATURE AT WHICH IT WILL EMIT RADIANT ENERGY OF A WAVE LENGTH THAT WILL PRODUCE A HIGH RATE OF HEATING IN SAID MATERIALS AND A LOW RATE OF HEATING IN SAID CARRIER; AND (C) CONTROL MEANS RESPONSIVE TO CHANGES IN THE CARRIER VELOCITY FOR MAINTAINING THE QUANTITIES OF THE RADIANT ENERGY SUPPLIED TO SUCCESSIVE LIKE INCREMENTS OF SAID CARRIED SUBSTANTIALLY EQUAL, SAID CONTROL MEANS INCLUDING MEANS FOR VARYING THE TOTAL FLUX OF THE RADIANT ENERGY IN PROPORTION TO CHANGES IN THE VELOCITY OF SAID CARRIER WITHOUT SUBSTANTIAL VARIATION IN THE WAVE LENGTH OF SAID RADIANT ENERGY BY VARYING THE EFFECTIVE LENGTH OF THE RADIANT ENERGY SOURCE MEANS. 